She paid for food and vet bills until it was rehoused with a police officer in 2010 - months before fresh investigations into illegal activities at the News of the World.

Details of the two-year loan come amid ongoing scrutiny over the close relationship between police and the media giant.

A Metropolitan Police spokesman earlier confirmed to the Press Association that riding enthusiast Ms Brooks was first given permission to take charge of the horse in 2008 but further details have been disclosed.

A police spokesman said: "In 2007 a request was made by Rebekah Brooks to home a retired police horse.

"Mounted Branch conducted the normal property and welfare inspection, which was passed. As a result 22-year-old retired horse Raisa was loaned to Rebekah Brooks in 2008.

"The MPS was contacted in early 2010 by an individual on behalf of Rebekah Brooks who asked the MPS to re-home Raisa, which was then 24, due to the horse no longer being ridden.

"When the horse was returned Raisa was regarded by officers from Mounted Branch to be in a poor but not serious condition."

The horse later died of natural causes.

The Police added: "When rehoming a retired MPS horse, the appropriate welfare checks are carried out by mounted branch officers."

The horse she borrowed was one of 12 retired by the force in 2008. A further 29 had their duties ended between 2009 and 2011.

Many of the animals are retired with The Horse Trust charity in Buckinghamshire.

Brooks, who is married to former racehorse trainer Charlie Brooks, remains on bail after being arrested and questioned by detectives last summer on suspicion of phone hacking and corruption, just days after resigning as chief executive.

The force said it informed the Leveson Inquiry about the information relating to Raisa on 14 February and these latest revelations come a day after a memo indicating Brooks was briefed by police on the original phone hacking investigation also emerged at the inquiry.

At Leveson on Monday, the officer at the head of the corruption investigation, Sue Akers, said The Sun newspaper had a "culture" of illegal payments to officials in all areas of public life.